1. Field of the Invention
The present invention relates to a rotor and, more particularly, to a rotor that can be applied to a miniature motor.
2. Description of the Related Art
Each of FIGS. 1 and 2 shows a conventional rotor, with the two rotors of said drawings being similar. Referring to FIG. 1, a conventional rotor is designated as “9” and includes a hub 91, a permanent magnet 92 mounted on an inner and axially extended wall of the hub 91, and a shaft 93 (or 93′ in FIG. 2) with two ends. A shaft seat 94 is formed on the center of and inside the hub 91. One end of the shaft 93 is a connecting end fixed to the shaft seat 94. Hence, the rotor 9 can be driven to revolve by a stator 82 while the other end of the shaft 93 rotatably extends through a bearing 81. It is noted that the major difference between rotors of FIGS. 1 and 2 is appearances of the connecting ends of the shaft 93 (seen in FIG. 1) and the shaft 93′ (seen in FIG. 2)
In general, as shown in FIGS. 1 and 2, the connecting end of the shaft 93, 93′ and the shaft seat 94 of the hub 91 are combined in two ways. One way is that the connecting end forms at least one concavity 95 (seen in FIG. 1), and the other way is that the connecting end forms impressed patterns 96 (seen in FIG. 2), with the connecting end of the shaft 93, 93′ being securely inserted into the shaft seat 94. Thus, combination of the connecting end of the shaft 93, 93′ and the shaft seat 94 is enhanced to prevent a departure of the shaft 93, 93′ and the hub 91.
The current trend of research and development in electronic products is miniaturization, and that results in the necessity of minimizing dimensions of motors. However, with a length of the shaft 93, 93′ being fixed, the rotor 9 will be liable to revolve unstably if the hub 91 has the shaft seat 94 or a thicker wall for receiving the connecting end of the shaft 93, 93′ while a part of the shaft 93, 93′ for coupling to the bearing 81 is shortened. On the other hand, if the part of the shaft 93, 93′ for coupling to the bearing 81 is lengthened, contact area between the shaft 93, 93′ and the hub 91 is reduced.
In conclusion, reduction of an axial height of the shaft seat 94 leads to reduced contact area between the shaft 93, 93′ and the hub 91, which causes weakness in combination of the shaft 93, 93′ and the hub 91. However, it is difficult to minimize dimensions of the motor without reduction of the axial height of the shaft seat 94. As a result, the conventional rotor 9 is not feasible for a miniature motor.